1. Technical Field
The present invention relates to a sealing device or plug for sealing off a elongated element, such as an cable, a pipe or an umbilical, at its entrance into an apparatus, in particular at the lower horizontal end of an offshore J-tube, leading from the sea bed up to a platform structure. The sea bed may be several hundred meters below the sea level.
2. Description of the Prior Art
In some cases it is desirable, after a elongated element has been installed within an J-tube, that the sea water surrounding the element within the J-tube is deoxidized to prevent or reduce corrosion of the element and of the inner walls of the tube. In order to neutralize the sea water in the tube, inhibiting agents are added to the water, and the inside pressure is normally some 5-6 bar more than the pressure of the surrounding water. A problem arises, however, due to difficulties in obtaining a full seal between the surface of the elongated element and the tube entrance. If the seal is poor,--the external sea water will be gradually exchanged with the inhibited sea water within the tube. A suitable sealing device should also prevent pollution that might be caused by leaking inhibiting agents into the sea.
From GB 2 188 999 B, there is known a sealing device or plug comprising at least two elements which are arranged to be pressed against each other, against a circumference of the elongated element and against the aperture of said apparatus. At least one of the elements is hinged to the apparatus
In GB 2 281 365 A, a sealing device or plug comprises centralizing means arranged around the elongated element inside a pull-in-flange at the lower entrance of the J-tube, sealing means arranged around the elongated element next to the centralizing means, and formed as a one-piece split annulus, the split being in a plane substantially parallel to the axis of the annulus and to the axis of the elongated element, and pressure means for pressing the sealing means to sealing contact against the elongated element, against the flange surface and against the centralizing means
In GB 2 297 59 A, a sealing device or plug consists of two substantially identical parts or halves which are hinged together along an axis substantially parallel to the axis of the elongated element, each half comprising a centralizer part, a sealing part and tensioning parts capable of pressing the sealing means to sealing contact against the elongated element, against the inner surface of the J-tube and against the centralizing means. There are described means for interlocking the two halves with each other and interlock the device with a bellmouth flange. There are also described separate interlockable two-part means for exerting a certain friction against the surface of the elongated element when the sealing parts are interlocked but not yet tensioned.
The technical problem is--as mentioned--to provide a reliable seal at the subsea entrance of an elongated element into a socalled J-tube bellmouth. The prior art solutions all rely on compression of rubber gaskets to obtain a suitable seal, but when the inside of the J-tube is rough it is difficult to obtain a good seal.